.TH std::experimental::ranges::less 3 "2024.06.10" "http://cppreference.com" "C++ Standard Libary"
.SH NAME
std::experimental::ranges::less \- std::experimental::ranges::less

.SH Synopsis
   Defined in header <experimental/ranges/functional>
   template< class T = void >

       requires StrictTotallyOrdered<T> ||
                Same<T, void> ||                                            (ranges TS)
                /* < on two const T lvalues invokes a built-in operator
   comparing pointers */

   struct less;
   template<>                                                               (ranges TS)
   struct less<void>;

   Function object for performing comparisons. The primary template invokes operator<
   on const lvalues of type T. The specialization less<void> deduces the parameter
   types of the function call operator from the arguments (but not the return type).

   All specializations of less are Semiregular.

.SH Member types

   Member type                                               Definition
   is_transparent (member only of less<void> specialization) /* unspecified */

.SH Member functions

   operator() checks if the first argument is less than the second
              \fI(public member function)\fP

std::experimental::ranges::less::operator()

   constexpr bool operator()(const T& x, const T& y)     \fB(1)\fP (member only of primary
   const;                                                    less<T> template)
   template< class T, class U >

       requires StrictTotallyOrderedWith<T, U> ||
                /* std::declval<T>() < std::declval<U>()     (member only of less<void>
   resolves to                                           \fB(2)\fP specialization)
                   a built-in operator comparing
   pointers */

   constexpr bool operator()(T&& t, U&& u) const;

   1) Compares x and y. Equivalent to return ranges::less<>{}(x, y);.
   2) Compares t and u. Equivalent to return std::forward<T>(t) < std::forward<U>(u);,
   except when that expression resolves to a call to a builtin operator< comparing
   pointers.

   When a call to \fB(1)\fP or \fB(2)\fP would invoke a built-in operator comparing pointers of
   type P, the result is instead determined as follows:

     * Returns true if the (possibly converted) value of the first argument precedes
       the (possibly converted) value of the second argument in the
       implementation-defined strict total ordering over all pointer values of type P.
       This strict total ordering is consistent with the partial order imposed by the
       builtin operators <, >, <=, and >=.
     * Otherwise, returns false.

   The behavior is undefined unless the conversion sequences from both T and U to P are
   equality-preserving (see below).

   Equality preservation

   An expression is equality preserving if it results in equal outputs given equal
   inputs.

     * The inputs to an expression consist of its operands.
     * The outputs of an expression consist of its result and all operands modified by
       the expression (if any).

   Every expression required to be equality preserving is further required to be
   stable: two evaluations of such an expression with the same input objects must have
   equal outputs absent any explicit intervening modification of those input objects.

.SH Notes

   Unlike std::less, ranges::less requires all six comparison operators <, <=, >, >=,
   == and != to be valid (via the StrictTotallyOrdered and StrictTotallyOrderedWith
   constraints).

.SH Example

    This section is incomplete
    Reason: no example

.SH See also

   less function object implementing x < y
        \fI(class template)\fP

.SH Category:
     * Todo no example
